7233629132domain: NAppears in sequencesa(n) = (1/(2n)) * Sum_{d|n} phi(d) * 2^(2n/d) + (2^((n-4)/2), if n is even).at n=16A058880Number of frieze patterns of length n under a certain group (see Pisanski et al. for precise definition).at n=19A123045a(n) = ceiling((2^n+n-1)/n).at n=37A373895